However, in this ERC project, Sims and his collaborators are even going a step further. At a pre-programmed time, the tag is released and floats to the surface to relay data. The second one uses a more sophisticated tag that sharks tow along. The first one uses a satellite transmitter attached to the fin of the shark: whenever the animal comes to the surface, the device relays data via messages to polar orbiting satellites. Usually, researchers track sharks with one of two methods.

To test this and other hypotheses and get insights into the sharks’ behaviour, Sims and his team need to collect lots of data. These are cold-bodied shark species such as blue sharks, which have a lower metabolic rate than warm-bodied sharks like shortfin makos, and therefore likely withstand hypoxia for short periods of time.Īs to what these sharks are doing in these dead zones, David Sims’ team hypothesizes that they are actively hunting hypoxia-tolerant cephalopods, such as deep-water squids and octopuses, as it represents a biomass of food that is less exploited.Īs part of their project, they will investigate to what extent different shark species hunt in the top layer where hypoxia-intolerant prey species are also compressed, and to what extent some of them may move into oxygen minimum zones to feed on hypoxia-tolerant prey, thus avoiding the surface-layer competition with other predators. Interestingly, scientists know that not all shark species spend all their time near the surface of these zones, but can also dive deep into the areas of lower oxygen and stay there for some time. Throughout this project, Sims is hoping to find the answer. What remains a mystery, however, is why sharks spend so much time in these zones, where they are ending up on hooks of long-line fishers in higher numbers. ‘If you've got less water in a barrel it's easier to catch the fish.’ ‘Essentially, it's the shooting fish in a barrel analogy,’ says Sims. Being compressed in a smaller volume makes them more vulnerable. In order to survive in these low-oxygen environments, sharks, tunas and other fish must stay relatively close to the surface most of the time, where oxygen levels are higher.

The fact that oxygen minimum zones are fishing hot spots is relatively easy to explain. Soon after, they discovered that oxygen minimum zones were areas of high catch of sharks and other fish, prompting them to investigate further the relationship between fisheries, predators and low oxygen levels. This prompted them to start tracking fishing vessels too, looking for a potential link between the two. They noticed that blue sharks moved from around the Azores Islands to West Africa, encountering an oxygen minimum zone there. Not long after, Sims and his team realised that not much literature was available on the topic of sharks in relation to their oceanic environment, so they founded the Global Shark Movement Project and started tracking sharks in the central Atlantic. He got into satellite tracking by trying to achieve a better understanding of the basking shark’s feeding habits. Twenty-five years ago, Sims started studying sharks in UK waters as part of his PhD. Watching this video you are accepting Youtube cookies policy

Deep blue shark tracker 2021